1. Fields of the Invention
This invention is directed to an inner cutter for electric shavers adapted for use in connection with an outer shearing plate for a cutting operation, more particularly an inner cutter for improving sharp cutting performance while retaining the effect of capturing long hairs to be cut.
2. Description of the Prior Art
It has been known that an inner blade in the form of a cutting edge having zig-zag configuration can increase the effect of capturing and shearing hairs as disclosed in U.S. Pat. No. 3,092,904. However, a further investigation into the mechanism of shearing hairs reveals that the above prior inner blade of a zig-zag configuration suffers the following shortcomings:
(i) such prior inner blade is found to be effective for cutting long hairs, but not to be satisfactory for cutting upright short hairs or effecting a close shave. This can be explained with reference to FIGS. 13 and 14 illustrating schematically the cutting mechanism for a short hair 13. As shown in FIG. 14, such short hair 13 entered through a given perforation 15 in an outer shearing plate 11 will have the increased chance of being cut by the inner blade 10 alone rather than by the cooperation with the cutting edge of the perforation. At this occurrence, the short hair 13, when it encounters the ridge of the inner blade 10 as shown in FIG. 13, is subject to slippage S.sub.0 along the side of the ridge to the adjacent groove as the inner blade 10 moves in one direction indicated by the arrow, which causes the short hair to be pushed forwardly by the inner blade 10 and cut at a point away from the skin 14, therefore remaining on the skin, requiring a further chance of being encountered by the inner blade.
(ii) its serration uniformly formed along the entire length thereof will certainly increase the contacting area with the outer shearing plate such that the inner blade is subject to an unduly increased load or resistance to the motion thereof.
(iii) the above uniform serration will increase the overall rigidity of the inner blade so as to fail to provide a comfortable cutting sound.